A grid polarizer has been known as a polarizer which can freely set a polarization plane (see Non-patent Document 1). This is an optical part having a grid structure in which a large number of linear metals (wire) are arranged in parallel in a constant cycle. In the case of such a metal grid, if the grid cycle is shorter than a wavelength of an incident light, a polarized light constituent parallel with the linear metal forming the metal grid is reflected while a perpendicular polarized light constituent transmits, which functions as a polarizer creating a uniaxial polarized light. Use of this grid polarizer as an optical part of an isolator in optical communication or as a part for increasing a utilization rate of light and for improving brightness in a liquid crystal display is proposed.
[Non-patent Document 1] H. Hertz “Electric Waves”, Macmillan & Company Ltd., London, 1893, p. 177
As a method for forming a grid structure, Patent Document 1 discloses a method in which metal is formed on a light transmissive substrate by deposition, sputtering, or ion plating, resist is applied thereon, photoengraving is carried, out and then, stripes of thin wires are formed by UHF-ECR plasma etching. Patent Document 2 discloses a method of depositing a copper thin film on one side of a light transmissive substrate and forming a grid pattern in which a large number of copper thin wires are disposed in parallel by ion-milling with photolithographic technology using photo-resist which is substantially equivalent to the light transmissive substrate in a refractive index when hardening. Since an etching process is employed for these methods, only a grid polarizer with a narrow area can be obtained (0.3 μm×0.07 μm for Patent Document 1,1-inch diameter for Patent Document 2).
[Patent Document 1] Japanese Patent Laid-Open No. 2003-66229
[Patent Document 2] Japanese Patent Laid-Open No. 2000-284117
Patent Document 3 discloses a producing method for a grid polarizer film having an anisotropic structure in which a portion with metal and a portion where the polymer film is exposed are alternately arranged in the stripe state by forming a metal film on a polymer film, uniaxially drawing a laminated body of the polymer film/metal film so as to generate a crack in the metal in a direction crossing the drawing direction. Resins used for the polymer film include thermoplastic resins such as polycarbonate, polyethylene terephthalate, polyethylene, polyvinyl chloride, polysulphone, poly allylate, polyethersulphone, cellulose diacetate, and cellulose triacetate; polymethylmethacrylate, and thermoplastic resins with small photoelastic coefficient known by trademark as ARTON and ZEONEX. However, with the method described in Patent Document 3, it is extremely difficult to control a width, shape and the like of a crack generated in the metal film, and there is a problem that a uniform optical characteristic is hard to be gained in a plane. Also, if the grid polarizer film obtained by this method is left in a high-temperature and high-humidity environment, the polymer film slightly shrinks and the polarizing characteristics might be changed.
[Patent Document 3] Japanese Patent Laid-Open No. 2001-74935